/Engine/Source/Runtime/GeometryCore/Public/MeshBoundaryLoops.h
Read out the span from loop[i0] to loop [i1-1] into an array. If bMarkInvalid, then these values are set to -1 in loop
static void ExtractSpan ( [TArray](API\Runtime\Core\Containers\TArray)< int > & Loop, int i0, int i1, bool bMarkInvalid, [TArray](API\Runtime\Core\Containers\TArray)< int > & OutSpan )